The term “access point” (AP) as used herein includes, but is not limited to, a base station, an access router (AR), a Node B, a site controller, or other interfacing device in a wireless environment that provides other stations with wireless access to a network with which the AP is associated.
The term “station” (STA) as used herein includes, but is not limited to, a wireless transmit/receive unit (WTRU), a user equipment, a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment.
Typically, a WLAN includes a plurality of APs, wherein each AP is capable of conducting concurrent wireless communications with appropriately configured STAs, as well as multiple appropriately configured APs or ARs, when configured in the “infrastructure mode”. Some STAs may alternatively be configured to conduct wireless communications directly to one another, i.e., without being relayed through a network via an AP. This is commonly known as “peer-to-peer mode” or “ad hoc mode”. Where a STA is configured to communicate directly with other STAs, it may also be configured to function as an AP. STAs can be configured for use in multiple networks, with both network and peer-to-peer communications capabilities.
In the infrastructure mode architecture, STAs are conventionally connected in a star-type topology to a central AP in order to communicate to each other or to connect to other external networks. Although this architecture has proven successful in the past, many factors, such as the increasing number of closely located APs, the increasing number of applications for a WLAN, and the fact that APs are restricted to public bands, have resulted in conventional infrastructure mode architectures becoming less desirable. Accordingly, other infrastructure mode topologies have evolved.
One topology is known as a “mesh” topology, in which WLAN nodes have two or more paths between them which enables the nodes to communicate directly with each other (i.e., as in the ad hoc mode) and to communicate indirectly with each other (via other nodes that relay information). A second topology is known as a “split” architecture, in which one or more access routers (ARs) or access controllers (ACs) are connected via an interconnection to APs present in the network. The ACs provide network-wide monitoring, improve scalability, and facilitate dynamic configurability. The logical interconnection may be a direct connection to the APs, a switched connection, or a routed network connection. The AC and the AP may be collocated in the same physical device.
In addition to exchanging configuration and control information with the APs, the ACs “split” or share certain functionalities with the APs that are conventionally provided solely by the APs. That is, functions typically provided by standalone or “fat” APs are removed from these APs and are provided by the AC(s). These split-function or reduced-function APs are referred to as “thin” APs. This architecture is similar to a UMTS architecture, where the AC is analogous to a central radio network controller (RNC) and the AP is analogous to a Node B connected to the RNC.
FIG. 1 is a diagram of a network 100 with an infrastructure mode architecture including a plurality of STAs 102a-102n communicating with a fat AP 104. This architecture is often referred to as a fat AP architecture because all of the medium access control (MAC) layer functionalities are located in the AP 104. The STAs 102 communicate with the AP 104, and with one another via the AP 104. The AP 104 incorporates a physical (PHY) layer 106, a real time (RT) MAC layer 108, and a non-real time (NRT) MAC layer 110.
FIG. 2 is a diagram of a network 200 with a split architecture, including a plurality of STAs 202a-202i, several APs 204a-204c, and an access controller (AC) 206. In the split network 200, certain AP functions are split away from the APs 204 and are provided by the AC 206. Although the AP functions may be split in any number of configurations, FIG. 2 shows one of the most common arrangements. The APs 204 terminate the infrastructure side of the wireless physical links, provide radio-related management, and provide all RT services to the STAs 202. The AC 206 provides the NRT management functions such as configuration, quality of service (QoS), access control, etc., for all of the APs 204. By sharing functionalities at a higher layer, a better coordinated deployment is possible.
The AP functional definitions made to support future AC-AP architectures must also be backward compatible to accommodate present-day devices. Since infrastructure mode networks are the present-day convention, it is noted that accommodating hybrid architectures, i.e., those networks with both fat APs and thin APs, will be a significant challenge for future networks.
An example of a pathological hybrid network 300 with both fat APs and thin APs is shown in FIG. 3. The network 300 includes a plurality of STAs 302a-302i; two thin APs, AP1 (304a) and AP2 (304b); a fat AP, AP3 (306); and an AC 308. AP3 306 provides all of its L2 MAC functionalities, including both the RT MAC 310 and the NRT MAC 312. In this deployment, the AC 308 manages all three APs 304a, 304b, 306. Accordingly, there is a conflict with redundancy in the NRT functionalities between the AC (NRT MAC 314) and AP3 306 (NRT MAC 312). This conflict is further aggravated in other network topologies such as, for example, mesh networks, wherein AP functionalities are distributed over the entire mesh network and wherein direct communication between ACs and APs is not always possible.
Accordingly, it is desirable to provide a method and apparatus to resolve functional conflicts that arise in WLAN architectures.